Essentially position switches and safety switches include a switch housing which an actuator attached thereto, which is also referred to as a drive or drive head. If this actuator, which is embodied for example as a roller plunger or a lever, as a pivoting lever or a rod lever or as spring bar is actuated, a switching element or switching unit arranged in the switch housing and effectively connected to the actuator is actuated.
With the appropriate positioning and installation, the actuation of the actuator, for example by the movement of a machine or the opening of a protective door, brings about a forced opening of the switching unit and of a monitoring circuit connected to it.
In the past the effect of the force on the drive head has proved to be problematic. On the one hand it is a matter of transmitting the force effect to actuate the switching element in a suitable, mechanical manner to a piston which initiates the switching of the switching element. On the other hand undesired force effects arise which must be captured by the switch or by the switching device containing the switch and are not able to be used to actuate it.
Previously the above-mentioned problem was resolved for example by screw fixings, so that the drives were fixed to the switch housing by screws. This led a plurality of easy-to-mislay small parts, such as screws for example, as well as to difficult and customer-unfriendly disassembly or assembly using at least one tool.
So-called bayonet connectors were likewise used for fixing drives to the housing. The disadvantage in such cases is that the bayonet connections are expensive to manufacture, and also they do not produce a connection which is free from play. A positive connection between the drive and the housing however proves to be indispensable in practice in most cases.
Push-in connections have also been developed in the past, with which the drives have been fixed to the housing a linearly-guided slider. These arrangements can be criticized for the small contact surfaces of the drive and of the housing, resulting in the connection not being very firm. In particular the safety or position switch with a sliding catch is especially susceptible to torsional forces.
Rim couplings have long been known for fixing control circuit devices into a mounting hole of a front panel. This involves couplings which mechanically connect the actuator with the switching element and the undesired force effect is dissipated via a front panel, which means that the rim coupling would not have to be protected from any undesired damage from transmitted forces.
DE 225 69 37 discloses a coupling for connection of front elements to the built-in components of electrical control circuit devices. The coupling is characterized by the end of a front element located behind the front panel being embodied as a cylindrical connecting piece onto which an annular cage formed onto the extension element is able to be pushed in which a locking ring is supported concentrically to allow rotation and prevent axial movement.